The following information is provided to assist the reader in understanding technologies disclosed below and the environment in which such technologies may typically be used. The terms used herein are not intended to be limited to any particular narrow interpretation unless clearly stated otherwise in this document. References set forth herein may facilitate understanding of the technologies or the background thereof. The disclosure of all references cited herein are incorporated by reference.
Functional biomaterials can be used to solve some of the most vexing diagnostic and drug-delivery challenges. One of the major classes of biomaterials designed to resolve such limitations in treatment is based on functionalized polynucleotides such as nucleic acids; including both deoxyribonucleic acids (DNA) and ribonucleic acids (RNA). Nucleic acid-polymer hybrids (NAPH), including, but not limited to, DNA and RNA-polymer hybrids, DNAPH and RNAPH respectively, are an important segment of this field, and well defined NAPH can be used for several emerging biomedical applications including responsive polymer assemblies, non-covalent linkers for protein-polymer hybrids, DNA adjuvants, sensors and drug delivery vehicles.
In a number of studies, reversible deactivation radical polymerization (RDRP) methods have been utilized for the preparation of bio-conjugates. In general, RDRP procedures exhibit tolerance towards functional monomers and functional groups present in nucleic acids and drugs. The three most common RDRP methods are atom transfer radical polymerization (ATRP), nitroxide mediated polymerization (NMP) and reversible addition fragmentation transfer (RAFT) systems, each of which allow unprecedented control over polymer properties such as dimensions (molecular weight), uniformity (polydispersity), topology (geometry), composition and functionality.
There are two methods to conjugate polymers to DNA. In “grafting-to” methods, the DNA and a preformed polymer are conjugated using high yield linking chemistries, frequently called “click” chemistry. In “grafting-from” methods, an initiator or transfer agent is immobilized onto DNA and a copolymer is formed through an in situ chain extension polymerization reaction. Technically, polymers conjugated to DNA in this method are graft copolymers but the method has also been referred to as “blocking-from”.
An advantage of “grafting-to” procedures is that the precise composition of the DNA and each polymer segment are known before conjugation. Currently the majority of DNA-polymer conjugates, wherein the polymers are prepared using RDRP, have utilized a grafting-to procedure using “click” chemistries. Even using high-yield “click” chemistry, however, significant effort must be expended for purification to remove unreacted reactants.
There have been a few studies of a “grafting from” or “blocking-from” strategy for making DNA block copolymers using either ATRP or reversible addition-fragmentation chain transfer (RAFT) polymerization. In those studies, the DNA was functionalized with an amine that could be reacted in solution with an activated ester on a molecule including the initiator or transfer agent functionality. The DNA with the randomly incorporated functionality was subsequently immobilized on gold surfaces or gold nanoparticles. After immobilization, the polymer was grown from the randomly incorporated functionality. As the polymers were grown from surfaces via the attached DNA, any direct analysis and characterization of the DNA block copolymers was precluded.
ATRP has also been used for “grafting-from” or “blocking-from” accessible amine groups on proteins that were modified by reaction with low molecular weight molecules including ATRP initiator functionality. The functionalization procedure was neither site specific nor quantitative.